1. Field of the Invention
The present invention relates to rotating electrical machines.
2. Description of the Related Art
One of the challenges in the design of electrical systems for automobiles relates to the generation of electrical power. With the increasing number of electrical features on automobiles comes the need for increased electric power generation. Thus, one challenge is to find an alternator which can provide this increased power with a minimum of adverse vehicle-level consequences (such as increased cost, increased mass, increased packaging volume, and the like).
Further, because the power consumption of most electrical loads on an automobile is independent of engine speed, the aforementioned increased need for electrical power exists down to engine idle. Because the power output of alternators is generally a function of the speed at which they are driven, a large electrical load at idle can be particularly difficult to supply.
One proposed solution to the above concerns is a so-called "hybrid" alternator. Such an alternator would contain a rotor which combines field windings (a conventional feature of almost all present alternators) with added permanent magnets. Several patents disclose hybrid alternators, including U.S. Pat. No. 3,555,327, issued to Terry; U.S. Pat. No. 4,980,595, issued to Arora; U.S. Pat. Nos. 4,882,515 and 4,959,577, issued to Radomski; U.S. Pat. Nos. 5,132,581 and 5,177,391, issued to Kusase; and U.S. Pat. No. 5,397,975, issued to Syverson.
Although those designs just mentioned may have desirable features, other designs may provide superior power output. Just as importantly, alternative designs may prove to be more manufacturable than those designs. Thus, an alternator which can provide improved power output, particularly at low speeds, and which can do so in a highly manufacturable design, will provide advantages over the prior art.